Cooling element for a heater exchange

ABSTRACT

The invention relates to a cooling element provided with louvers to be used in a heat exchanger under the influence of passing cooling medium used for cooling another medium flowing inside a circulating element whereto the cooling element is bounded by a contact area on one edge, and the louvers form an angle with the surface of the cooling element. According to the invention the cooling element is positioned so that the cooling element forms a substantially equal angle to the longitudinal direction of the circulating element as the louvers form to the surface of the cooling element.

The invention relates to a cooling element provided with louvers to beused in a heat exchanger, particularly in a heat exchanger constructedso that the cooling element is under the influence of passing coolingmedium, as air or water, used for cooling another medium flowing insidea circulating element and that the cooling element is used as aconnecting member for two circulating elements.

In heat exchangers used in automotive industry for cooling a motor in avehicle, a fin is generally made of a corrugated strip. The corrugatedstrip itself is made of copper, copper-based alloy or aluminium oraluminium-based alloy and this corrugated strip is installed betweencirculating elements where medium to be cooled is circulated. Thecorrugated strip has a strong metallic bond with these circulatingelements of medium to be cooled. The metallic bond is made by a braze ora solder material. One corrugated strip creates many cooling elements,fins, between circulating elements and the fins are provided withlouvers for improving heat transfer capacity. Further, the finspositioned between two circulating elements are installed substantiallyperpendicularly to the longitudinal direction of the fin strip. Whenthese kind of fins are cut in the middle between the two circulatingelements, each individual fin has a number of louvers twisted at anangle of 20 to 45 degrees and grouped together in even numbers ofdifferent areas. Every odd area has the louvers at its angle and evenareas at the opposite angle. The louvers are very small, from 0.75 to1.5 millimeter, but the louvers are very efficient for the heat transfercapacity.

When cooling medium, as air or water, is passing the fins, coolingmedium is forced to flow in accordance with a flow pattern defined bythe louvers. At low cooling medium flow levels, the flow has in spite oflouvers space enough to go directly through the fins. On the contrary,at moderate or high cooling medium flow levels, the flow has to beredirected several times when passing the fins. This means more costsbecause of energy loss and this effect can be measured as a higherpressure drop over the heat exchanger.

The object of the present invention is to eliminate some drawbacks ofthe prior art and to achieve a cooling element to be used in a heatexchanger, particularly in a heat exchanger where the cooling element,as a fin, is a connecting member between two circulating elements sothat the redirections of a cooling medium as well as a pressure drop aresubstantially eliminated. The essential novel features of the inventionare apparent from the appended claims.

In accordance with the invention a cooling element, as a fin, in a heatexchanger is provided with louvers in order to improve heat transfercapacity in the heat exchanger. The fin is positioned betweencirculating elements of the heat exchanger so that a cooling medium, asair or water, passes the fin, and the fin will further cool thecirculating elements where another medium to be cooled flows. The fin isbond by a contact area on one edge to a circulating element, and thelouvers form an angle with the surface of the fin. The fin is installedbetween the two circulating elements so that the fin forms essentiallythe same angle towards the longitudinal direction of the circulatingelement as the louvers form towards the surface of the fin. This kind ofa fin arrangement eliminates redirections at moderate or high coolingmedium flow levels, because the louvers are essentially in the samedirection as the flow direction of the cooling medium when entering theheat exchanger. For high heat transfer capacity several fins areinstalled between two circulating elements.

The fins are installed between circulating elements so that between thefins and the circulating element there is advantageously a strong bondmade of a brazing or soldering material in the area where the fin andthe circulating element have a contact with each other. The fins areinstalled so that at least on the contact area with the circulatingelements the fins are advantageously essentially parallel to each other.In this contact area the fin forms an acute angle towards thelongitudinal direction of the circulating element. The acute angle is inthe range of 20 to 45 degrees, advantageously in the range of 25 to 35degrees. The angle of the fin towards the longitudinal direction of thecirculating element is dependent on the angle of the louvers to thesurface of the fin. This is because these two angles are substantiallythe same in largeness.

The fins can be positioned to the contact area with the circulatingelements so that the contact area with the circulating elements forms ashape of a straight line on its substantially whole length. The fins canalso be positioned so that the contact area with the circulatingelements forms a shape of a fraction line so that each part of thefraction line forms an substantially equal angle towards thelongitudinal direction of the circulating element.

The fins are advantageously created by a corrugated strip which isinstalled between two circulating elements so that the folds of thestrip have alternately a contact with one circulating element. The stripis further positioned so that in the contact area between the fold andthe circulating element the folds are substantial parallel to each otherand the folds form an acute angle towards the longitudinal direction ofthe circulating element.

The fin can also be a flat plate which has a connection between severalcirculating elements. In that embodiment the louvers are installedbetween the circulating elements so that a flow of cooling medium goesthrough the louvers when passing the flat plate shaped as a fin.

The fins and the corrugated strip for a creation of the fins areadvantageously made of copper, a copper-based alloy, aluminium or analuminium-based alloy.

The invention is described in more detail with reference to the appendeddrawings, where

FIG. 1 is a schematical side-view illustration of fins in the prior art,

FIG. 2 is an illustration of FIG. 1 seen from the direction A—A,

FIG. 3 is a schematical and partial top-view illustration of oneembodiment of the invention, and

FIG. 4 is a schematical and partial top-view of another embodiment ofthe invention.

In accordance with FIGS. 1 and 2 the fins 1 are positioned between twocirculating elements 2. The fins 1 are installed substantiallyperpendicular to the longitudinal direction 3 (shown as an arrow) of thecirculating element 2. The fins 1 are provided with louvers 4. Thelouvers 4 will make curves for cooling medium passing the fins 1 shownas an arrow 6 for high cooling medium flow level, but not for lowcooling medium flow level shown as an arrow 5.

In FIGS. 3 a and 3 b positions of louvers 12 in a fin 11 and the fin 11to the longitudinal direction 13 (shown as an arrow) of a circulatingelement 14 are illustrated. An angle of a louver 12 to the direction ofthe fin 11 is essentially equal to an angle of a fin 11 to thelongitudinal direction of the circulating element 14. The direction ofthe fin 11 is essentially the same in the essentially whole breadth 15of the circulating element 14. The fins 11 are positioned substantiallyparallel to each other. FIG. 3 b illustrates the angle B of oneindividual fin 11 relating to the circulating element 14 and the angle Cof one individual louver 12 relating to the surface of the fin 11.

FIG. 4 illustrates an embodiment where a fin 21 with louvers 25 changesits direction to the longitudinal direction 22 (shown as an arrow) of acirculating element 23, but an angle to the circulating element 23 isessentially the same in the essentially whole breadth 24 of thecirculating element 23.

1. A heat exchanger comprising: first and second elongate circulatingelements each having a longitudinal direction and each defining aninterior space for conducting a flow of heat exchange medium in saidlongitudinal direction, and a cooling element having a surface and alsohaving a contact area at one edge, wherein the cooling element is bondedat its contact area to the first circulating element and is providedwith louvers that are disposed at a first predetermined acute angle tothe surface of the cooling element, wherein the cooling element is partof a corrugated strip having alternating contact areas contacting thefirst and second circulating elements respectively, the cooling elementin disposed at a second predetermined acute angle to the longitudinaldirection of the first circulating element, and the first and secondpredetermined acute angles are substantially equal in magnitude.
 2. Aheat exchanger according to claim 1, wherein the magnitude of the secondpredetermined acute angle is in the range from 20 to 45 degrees.
 3. Aheat exchanger according to claim 1, wherein the contact area issubstantially rectilinear over substantially its entire length.
 4. Aheat exchanger according to claim 1, wherein the cooling element is madeof copper, a copper-based alloy, aluminum, or an aluminum-based alloy.5. A heat exchanger according to claim 1, wherein the cooling element isa fin.
 6. A heat exchanger according to claim 5, wherein the fin isdisposed at an angle 45° to the longitudinal direction of the firstcirculating element and cooling medium enters the heat exchanger in adirection substantially parallel to the louvers.
 7. A heat exchangercomprising: first and second elongate circulating elements each having alongitudinal direction and each defining an interior space forconducting a flow of heat exchange medium in said longitudinaldirection, and a cooling element composed of first and second portionseach having a surface and each also having a contact area at one edge,wherein each portion of the cooling element is bonded at its contactarea to the first circulating element and is provided with louvers, thelouvers of the first portion of the cooling element are disposed at afirst predetermined acute angle to the surface of the first portion ofthe cooling element, and the louvers of the second portion of thecooling element are disposed at a second predetermined acute angle tothe surface of the second portion of the cooling element, wherein thefirst portion of the cooling element is disposed at a thirdpredetermined acute angle to the longitudinal direction of the firstcirculating element, the second portion of the cooling element isdisposed at a fourth predetermined acute angle to the longitudinaldirection of the first circulating element, and the first, second, thirdand fourth predetermined acute angles are substantially equal inmagnitude.
 8. A heat exchanger according to claim 7, wherein themagnitudes of the third and fourth predetermined acute angles are eachin the range from 20 to 45 degrees.
 9. A heat exchanger according toclaim 7, wherein the contact areas of the first and second portions ofthe cooling element are each substantially rectilinear oversubstantially its entire length.
 10. A heat exchanger according to claim7, wherein the cooling element is made of copper, a copper-based alloy,aluminum, or an aluminum-based alloy.
 11. A heat exchanger according toclaim 7, wherein the cooling element is a fin.
 12. A heat exchangeraccording to claim 11, wherein the fin is disposed at an angle 45° tothe longitudinal direction of the first circulating element and coolingmedium enters the heat exchanger in a direction substantially parallelto the louvers.